A mechanical seal with bellows is known as a shaft seal device of a pump that handles fluid of high temperature over 200° C. and containing great amount of solid content such as asphalt, tar, pitch, and the like in petroleum refinery, petrochemical plant, iron making chemical plant, and the like (see non-patent document 1).
The bellows type mechanical seal will be described with reference to FIG. 6 to FIG. 8. FIG. 6 is a schematic cross-sectional view describing the configuration of the bellows type mechanical seal according to the conventional example. FIG. 7 is a view seen from X of FIG. 6. FIG. 8 is a schematic cross-sectional view describing the configuration of the bellows type mechanical seal according to another conventional example.
A mechanical seal 100 shown in FIG. 6 has a configuration in which a seal ring 102, which is resiliently supported by a housing 200 through a retainer 104, a bellows 101, a collar 105, a seal cover 202, and the like, and a mating ring 103 fixed to a rotating shaft 300 contact in a freely slidable manner with each other to seal an annular space between the housing 200 and the rotating shaft 300.
The seal ring 102 is burn fitted or press fitted to the retainer 104 welded to one end of the bellows 101. The collar 105 is welded to the other end of the bellows 101. The collar 105 is fixed to the seal cover 202 attached to an opening of a shaft hole 201 of the housing 200. The mating ring 103 is fixed to a sleeve 301 fixed to an outer circumferential surface of the rotating shaft 300.
The seal ring 102 and the mating ring 103 are arranged axially lined so that the end faces of the seal ring and the mating ring perpendicular to the shaft contact with each other, and are configured to slidably move in the circumferential direction to each other where when the rotating shaft 300 rotates with respect to the housing 200. The seal ring 102 has higher follow-up property with respect to the mating ring 103 as the bellows 101 resiliently receive the slidable movement torque generated by the slidable movement with the mating ring 103.
A baffle sleeve 203 for guiding the quench fluid such as steam to the end sealing face, cleaning the oozed and leaked solution from the end sealing face, and cooling and lubrication of the end sealing face is also arranged. The baffle sleeve 203 is attached to the seal cover 202, and includes a cylindrical portion 203a extending axially on the inner diameter side of the seal ring 102 and the mating ring 103.
As shown in FIG. 7, a damper 109a configured by a plurality of projections projecting out in the inner diameter direction is arranged on the inner peripheral surface of the retainer 104. The damper 104a is projected out so as to partially narrow the space between the inner peripheral surface of the retainer 104 and the outer peripheral surface of the cylindrical portion 203a of the baffle sleeve 203 in a range the axial movement of the retainer 104 is not inhibited. The movement in the direction perpendicular to the shaft in the retainer 104 is thereby regulated, the occurrence of circumferential microscopic vibration (stick slip) of high cycle at the end sealing face due to lack of lubricant at the end sealing face and the like is suppressed, and the breakage of the welded portion of the bellows 101 by the vibration is prevented.
However, in the configuration in which the seal ring 102 is burn fitted or press fitted to the retainer 104 so as to be integrated, lowering of sealability, damage due to local contact at the end sealing face etc. occur from the influence of the difference in coefficients of thermal expansion of the bellows 101, the seal ring 102, and the retainer 104 at the time of high temperature use.
In the mechanical seal 100′ shown in FIG. 8, the seal ring 102′ is not fixed to the retainer 104′, and they are contacted at the lapped (surface polished) surfaces. Thus, the influence of the difference in coefficients of thermal expansion can be reduced, the sealability can be maintained even at the time of high temperature use, and damages due to the influence of heat deformation and the like can be suppressed. Furthermore, special steps such as burn fitting and press fitting, and the subsequent heat processing and the like are unnecessary, so that the manufacturing cost can be reduced.
In such mechanical seal 100′, a projection 203b arranged at the distal end of the cylindrical portion 203a of the baffle sleeve 203′ is loosely engaged to the cutout 102a formed on the inner peripheral surface of the seal ring 102′, so that the baffle sleeve 203′ clutches the seal ring 102′. The slidable movement torque thus is prevented from being transmitted to the bellows 101.
A damper 104a′ or a plurality of projections projecting in the inner diameter direction is arranged on the inner peripheral surface of the retainer 104′. The damper 104a′ is projected out in the inner diameter direction so as to partially narrow the space between the retainer 104′ and the cylindrical portion 203a of the baffle sleeve 203′ in a plurality of areas on the inner peripheral surface of the retainer 104′ to regulate the movement of the retainer 104′ in the direction perpendicular to the shaft and suppress the oscillation of the bellows 11, similar to the damper 104a of the mechanical seal 100 shown in FIG. 6.
Furthermore, an annular recess is formed by a step difference portion 102b and a stepped portion 104b for partially reducing the outer diameter is formed at the outer peripheral surface of the seal ring 102′ and the outer peripheral surface of the retainer 104′, and a centering case 106 for centering the seal ring 102′ and the retainer 104′ is attached to the recess.
However, since the centering case 106 is fitted with a very small gap in view of the change in dimension by thermal expansion, the vibration is transmitted to the bellows 101 when fluid such as tar and pitch enters the space and is fixed thereat, thereby damaging the bellows 101.